I have seen the Red Army Choir, they are considered really top (and they seem to have outlasted the actual army). everything else I have bought or seen is just small church music. I am not familiar with Russian Opera, but if it inlcudes the unusual tone that is common to Russian church music and you enjoy it you might want to look for orthodox religious music
I have a few CDs with russian basso profundus. Amazing vocal range. There is a special something about Russian music. Ilya Gringolts commented that it's very honest, every note is suffered through. That is very much true given that Russians are big time pros at suffering.